What is CVE-2026-9903?

CVE-2026-9903 is a medium-severity vulnerability in Google Chrome, classified under Improper Input Validation. CVSS score: 5.0/10. Published 2026-05-28.

How severe is CVE-2026-9903?

Medium severity. CVSS v3 base score is 5.0 out of 10.

Improper input validation in Google Chrome

CVE-2026-9903

Insufficient validation of untrusted input in Site Isolation in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted MHTML page. (Chromium security…

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

EPSS: 0.000 (9.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.0 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L.

Affected products

Google Chrome — versions 148.0.7778.216

Weakness classification (CWE)

CWE-20 — Improper Input Validation

References

chrome-cve-admin@google.com (Release Notes)
chrome-cve-admin@google.com (Permissions Required)

Frequently asked questions

What is CVE-2026-9903?: CVE-2026-9903 is a medium-severity vulnerability in Google Chrome, classified under Improper Input Validation. CVSS score: 5.0/10. Published 2026-05-28.
How severe is CVE-2026-9903?: Medium severity. CVSS v3 base score is 5.0 out of 10.